1. Field of the Invention
The present invention relates to self-propelled, walk-behind lawnmowers for cutting grass which also incorporate a shredder or chipper.
2. Summary of the Prior Art
Push-behind lawnmowers with a powered cutting mechanism are well-known. Mowers of this type normally include a generally centrally located deck or housing that includes a skirt which runs around the perimeter of the deck or housing, and a powered cutting mechanism such as a pair of rotating blades, or blades attached to a rotating cutting disc, located under the deck and skirt. Items such as the engine or power source for the blades are generally located above the deck, attached to the top of the deck. The area bounded by the deck and skirt generally forms a cutting area.
Mowers usually also include a clippings catcher which catches cut grass clippings. This is normally located at the rear of the mower, attached to the rear of the deck or housing.
While so-called hover mowers are known, such as those produced by ‘Flymo’, most mowers also include wheels, usually located at the corners of the deck.
Generally, there are two main ways in which mowers can be powered—electrically or by a petrol motor. Electric mowers are usually powered by an electrical cable connected between the mower and a mains outlet. Petrol powered mowers are generally known as motor mowers, with the motor included as part of the mower so the mower is self-contained or self-sufficient.
It is usual for the cutting mechanism to be formed as a disc that includes at least a pair of cutting blades, aligned at 180 degrees to one another to rotate around a central point, the tips of the blades forming a cutting circle or cutting disc as they rotate. The power for the cutting mechanism is provided from a power source to the cutting mechanism. The power source is generally located on top of the deck (e.g. the motor), and a drive shaft extends downwards through the deck to power the cutting blades. For ‘push’ type or user-propelled mowers of either the electric or motor mower type, a user is required to push the mower in order to move it in the direction in which they wish to proceed—the power source does not provide movement power for the mower as a whole, just the cutting mechanism. However, for some mowers, such as the ‘Masport® series 19 MSV 550 self-propelled’, power is also drawn from the motor in order to propel the mower forwards, a user controlling the movement direction of the mower by pushing the handle, and the speed of both the mower and (if required) the blades by way of controls on the mower handle. Mowers of this type are generally known as self-propelled mowers.
As the mower moves forward, the tips of the blades contact the grass and cut it. The motion of the blades flings the grass clippings around the inside of the mower cutting area under the deck and towards the rear of the mower in a slingshot effect. The Masport® series 19 mowers are designed to take advantage of this effect, by having a deck with an overall volute shape, with one side of the deck formed as an expanding funnel. The motion of the blades causes the grass clippings and the surrounding air to be channelled along this funnel and out of the rear of the mower. In order to maximise this effect and to increase efficiency it is important that this channel is smooth and that there are no internal impediments which might disrupt the air flow or prevent the grass clippings from being thrown to the rear of the mower.
As well as cutting grass, some types of push mowers may also be adapted to dispose of heavier garden waste or garden refuse such as a small branches or similar. This is useful where a user may not require a dedicated static chipper/shredder unit such as are known in the industry, but where the user may encounter circumstances or situations where as well as cutting the grass, they need to quickly and easily deal with or dispose of other, heavier types of garden refuse such as small windfall branches or similar. It is known to incorporate a small chipper or shredder into push mowers so that a user can achieve this. An example of a push mower that incorporates a chipper/shredder would be the ‘Masport® series 19 MSV 3′N′1 Combo’. This is a user-propelled or ‘push’ type mower that includes a chipper shredder. A chipper tube is located on the top of the housing, aligned upwards and angled slightly backwards towards the mower handle. If a user needs to dispose of garden refuse such as small branches or similar, these are dropped or pushed into the top of the tube, passing down the tube into the cutting area under the housing and skirt. The ‘Masport® series 19 MSV 3′N′1 Combo’ includes a second, heavier, chipping or shredding disc or pair of blades located above the grass cutting blade, with both blades powered by a single drive shaft directly connected to the motor which is located on top of the housing, so that the grass cutting blades and the chipping blades rotate around a single axis. Refuse passing down the tube and entering the cutting area will contact the heavier chipping blades first. This refuse is chipped or shredded by the upper cutting blade or blades, and the resulting chips are disposed of in the same manner as the grass clippings produced by the lower grass cutting blade are disposed of. In the ‘Masport® series 19 MSV 3′N′1 Combo, clippings are disposed of by being flung or thrown by the cutting blades around the outside perimeter of the cutting space in a centrifugal manner in a similar manner to how grass clippings are disposed of as outlined above. In order to aid in this disposal and centrifugal style throwing of clippings, the interior space under the deck and skirt (the cutting area) is volute-shaped in the Masport® Series 19 mowers. The mower deck includes an exit aperture at the rear to which a catcher can be connected in use. The chippings and grass clippings are flung around the outside perimeter of the cutting space and through this aperture. With a catcher connected to the rear of the mower, the chippings and grass clippings are collected in the catcher.
For mowers which include a chipper/shredder, where both the grass cutting blades and the chipper blades are arranged to rotate about a single axis, it is highly desirable that the deck is configured in such a manner that the rotation of the blades will sweep grass clippings and chippings around the cutting space and then into a collector or similar. In the Masport® Series 19 mowers, this is achieved by shaping the deck as a volute, as noted above, with an exit aperture extending across the rear of the mower. The clippings and chippings are swept in a circular motion around the volute and then flung backwards (and possibly slightly sideways across the mower from one side to the other), through the exit aperture and then into a collector at the rear—a circumferential slingshot effect. The exit aperture in the Masport® Series 19 mowers extends across the whole of the rear of the mower so that this sweeping effect can be achieved smoothly. It should be noted that it is desirable that the exit aperture extends at least to the centreline of the mower, so that all (or at least as much as possible) of the waste created is swept through the aperture as the cutting blades rotate.
From this, it can be seen that in mower which include a chipper/shredder, it is desirable to offset the chipper/shredder tube to one side—to the opposite side to the exit aperture and the funnel of the volute. This allows the exit aperture to be formed as large as possible, and for the exit aperture to extend across the body of the mower at least as far as the centre line of the mower, and possibly further than the centre line if the chipper tube is offset forwards. Also, it should be noted that generally chippings created by the chipper will be heavier than grass clippings, and it is highly desirable that the outer end or ends of the blades are used to sweep chippings through the cutting space, as the outer ends of the blades will be travelling fastest, and these will therefore impart as much kinetic energy to the chippings as possible. This helps ensure that the chippings have enough velocity to be thrown cleanly through the exit aperture, without dropping down through the cutting space onto the ground before reaching the exit aperture. It is therefore desirable to offset the chipper tube to one side, so that the outer ends of the blades are in general the part of the blade that contacts the items which a user is inserting into the chipper tube for chipping or shredding. It is also desirable that the ends of the blades are used for chipping and shredding, as these will be moving faster, have more energy, and will chip and shred items more easily than the inner part of the blade or blades. It should be noted that the inner (cutting space) end of the chipper tube is almost impossible to locate on the same side as the main portion of the exit aperture—i.e. within the expanding funnel of the volute. If the tube is located on this same side, then it will interfere greatly with the funnel or volute effect, as it will be required to extend downwards into the funnel so that the lower end is close to the chipping blade. Furthermore, it will either be too far back on the deck to fall within the ‘sweep’ of a single blade or blades rotating around a common axis to form a cutting disc (outside the circumference of the cutting disc), or if the tube is located forward (and within the blade sweep), it may also tend to sweep the chippings past the exit aperture so that they have to be swept in a full circle all the way around the cutting area before they can be thrown through the exit aperture. This increases the risk that they will fall out underneath the mower before they can be swept all the way round again to the exit aperture. These ‘older’ chips will also interfere with new material being fed through the tube, and this also increases the chance of chips falling out of the bottom of the mower rather than being thrown through the exit aperture. It also makes it harder for the mower deck to be formed as a compact item, with as little surface area as possible.
For self-propelled mowers, it is highly desirable to power the grass cutting blades, and the (self-)propelling mechanism from a single power source. This reduces costs and complexity. It is also highly desirable for the mechanism by which power is provided from the motor to the self-propelling source to be as simple as possible, and also for this mechanism to provide power evenly to the wheels at both sides (and possibly both ends) of the mower. That is, to provide the same torque and speed simultaneously to each of the powered wheels (usually the rear wheels only) so that the mower is not constantly pulling to one side in use and a user does not constantly have to pull the mower back on course.
In order to achieve the use of a single motor or power source to power both the blades and the wheels, a power off-take mechanism of some sort is normally used. In push type mowers, the grass cutting blades are powered e.g. by a direct drive shaft connection to the motor drive shaft. In self-propelled mowers, a power take-off mechanism such as a belt drive is used to ‘take-off’power from the motor to the wheels, the belt drive connected to a gear box or similar so that power can be provided to the wheels, this arrangement also ensuring that power is evenly distributed to all the drive wheels (e.g. both rear wheels). It is highly desirable to locate the gearbox to one side—the opposite side to the funnel of the volute, so that it interferes as little as possible with the other elements of the mower such as the exit aperture, and so that the mower deck can be as compact as possible.
For the reasons outlined above, it is highly undesirable to locate the gearbox (or similar item) on the same side as the exit aperture. However, it is highly desirable to locate it to one side (rather than centrally) as this allows the exit aperture to extend across as much of the rear of the mower as possible, preferably at least as far as the centre line, or even more preferably the total width of the rear deck. This also allows the mower deck to be as compact as possible.
As outlined above, mowers that are self-propelled are known. Push type mowers that include a chipper/shredder for the disposal of heavier garden waste such as small windfall branches are also known. However, as can be seen from the above, combining self-propelled mowers with mowers that also include a chipper/shredder presents a number of problems, as fulfilling the desired requirements for one is mutually contradictory with the requirements for the other.
The term “comprising” as used in this specification means “consisting at least in part of”. When interpreting each statement in this specification that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner.